The present invention relates to a variable displacement swash plate type compressor adapted for use in an air conditioning system for a vehicle, and more particularly to a compressor conduit means for pressurizing a crankcase to control the displacement of the swash plate of the compressor, and for facilitating lubrication of compressor components.
Variable displacement swash plate type compressors typically include a cylinder block provided with a number of cylinders, a piston disposed in each of the cylinders of the cylinder block, a crankcase sealingly disposed on one end of the cylinder block, a rotatably supported drive shaft, and a swash plate. The swash plate is adapted to be rotated by the drive shaft. Rotation of the swash plate is effective to reciprocatively drive the pistons. The length of the stroke of the pistons is varied by the inclination of the swash plate. Inclination of the swash plate is varied by controlling the pressure differential between a suction chamber and a crank chamber. The pressure differential is typically controlled using a control valve and an orifice tube which facilitates fluid communication between a discharge chamber and the crank chamber to convey compressed gases from the discharge chamber to the crank chamber based on pressure in a suction chamber.
The compressor arrangement in the prior art described above has several disadvantages. First, due to the introduction of refrigerant gas through the orifice tube into the crank chamber, the pressure within the crank chamber cannot be accurately controlled. Second, when the compressor is operating at maximum capacity, the control valve closes, thereby eliminating flow through the orifice tube. Therefore, ineffective lubrication of the close tolerance moving parts within the crank chamber occurs due to the lack of consistent flow of refrigerant gas from the discharge chamber to the crank chamber. Finally, the tight tolerances required in the orifice tube are difficult to achieve in manufacturing due to the small diameter of the orifice tube.
An object of the present invention is to produce a swash plate type compressor wherein the pressure within the crankcase is increased and efficiently controlled.
Another object of the present invention is to produce a swash plate type compressor wherein oil flow to the crankcase during both minimum and maximum operating conditions is facilitated to result in improved lubrication of the compressor components.
The above, as well as other objects of the invention, may be readily achieved by a variable displacement swash plate type compressor comprising: a cylinder block having a plurality of cylinders arranged radially therein; a piston reciprocatively disposed in each of the cylinders of the cylinder block; a cylinder head attached to the cylinder block; a crankcase cooperating with the cylinder block to define a crank chamber; a drive shaft rotatably supported by the crankcase and the cylinder block; a swash plate adapted to be driven by the drive shaft, the swash plate having a central aperture for receiving the drive shaft, radially outwardly extending side walls, and a peripheral edge; and conduit means providing fluid communication between the crank chamber and at least one of the cylinders of the cylinder block.